Quantifying coronary microvascular disease: assessing absolute microvascular resistance reserve (MRR) by continuous coronary thermodilution

Background and aim

Hyperemic absolute coronary blood flow (in mL/min) can be safely and reproducibly measured with intracoronary continuous thermodilution of saline at room temperature at an infusion rate of 20 mL/min. This study aims at assessing whether continuous thermodilution can also measure resting flow and microvascular resistance.

Methods and results

In 87 coronary arteries (58 patients) with angiographic non-significant stenoses absolute flow was assessed by continuous thermodilution of saline at infusion rates of 10 mL/min and 20 mL/min using a pressure/temperature sensored guide wire, a dedicated infusion catheter and a dedicated software. In addition, in 26 arteries, average peak velocity (APV) was measured simultaneously using an intracoronary Doppler-wire.

There was no significant difference between Pd/Pa at baseline and during saline infusion at 10 mL/min, (0.95±0.053 vs 0.94±0.054, respectively (p=0.53) and there was no significant difference in APV at baseline and during the infusion of saline at 10 mL/min (22.2±8.40 vs 23.2±8.39 cm/s, respectively, p=0.63), thus indicating presence of resting coronary blood flow during the infusion of 10 mL/min of saline.

In contrast, at an infusion rate of 20 mL/min, a significant decrease in Pd/Pa was observed compared to baseline: (0.85±0.089 vs 0.95±0.053, respectively, p<0.001) and a significant increase in APV was observed (22.2±8.4 cm/s to 57.8±25.5 cm/s, respectively, p<0.001). The coronary flow reserve (CFR) calculated by thermodilution and by Doppler flow velocity were similar (2.73±0.85 vs 2.72±1.07, respectively) and their individual values correlated closely (r=0.87, 95% CI 0.72–0.94, p<0,001). Microvascular resistance (Rμ), defined as the distal coronary pressure divided by the absolute flow was calculated both at rest (Rμ-rest) and during hyperemia (Rμ-hyper). Microvascular Resistance Reserve (MRR), is calculated as the ratio of Rμ-rest and Rμ-hyper and showed a good correlation with the analogous Doppler-derived parameter (using the APV instead of absolute flow). Mean doppler and thermodilution derived MRR were similar (3.32±1.50 vs 3.23±1.16) and values correlated closely (r=0.91, 95% CI 0.81 - 0.96, p<0.001; Bland-Altman analysis: mean bias = 0.071, limit of agreement −1.195 to 1.338).

Conclusion

Absolute coronary blood flow (in mL/min) can be measured by continuous thermodilution both at rest and during hyperemia. This allows accurate, reproducible, and operator-independent direct volumetric calculation of CFR and MRR. The latter is a quantitative metric which is specific for microvascular function and independent from myocardial mass.

Doppler and Thermodilution derived MRR

Funding Acknowledgement

Type of funding source: None

Diagnosis of heart failure with preserved ejection fraction in patients with dyspnea and paroxysmal atrial fibrillation: a role of left atrial strain

Background

Diagnosis of heart failure with preserved ejection fraction (HFpEF) in patients with dyspnea and paroxysmal atrial fibrillation (AF) is challenging. Speckle tracking-derived left atrial strain (LAS) provides an accurate estimate of left ventricular filling pressures and left atrial phasic function. However, data on clinical utility of LAS in patients with dyspnea and AF are scarce.

Objective

To assess relationship between LAS and probability of HFpEF in patients with dyspnea and paroxysmal AF.

Methods

The study included 205 consecutive patients (62±10 years, 58% males) with limiting dyspnea (NYHA ≥ II), paroxysmal AF and preserved LVEF (≥50%), who underwent speckle tracking echocardiography and natriuretic peptide (NT-proBNP) assessment during sinus rhythm. Patients with manifest ischemic heart or valve disease, and cardiomyopathy were excluded. Probability of HFpEF was estimated using H2FPEF and HFA-PEFF scores, which combine clinical characteristics, echocardiographic parameters and natriuretic peptides.

Results

A total of 61 (30%), 115 (56%) and 29 (14%) had respectively high, intermediate and low probability of HFpEF. Patients with high probability of HFpEF were significantly older, had higher body mass index, NT-proBNP, E/e', pulmonary artery pressure and larger LA volume index than patients in low-to-intermediate probability groups (all p<0.05). Two distinct patterns of LA phasic function were observed. Firstly, reservoir LAS showed close inverse association with increasing probability of HFpEF. Secondly, contractile LAS showed initial decrease with subsequent compensatory increase in intermediate probability category with final decrease in patients with high HFpEF probability. In contrast, LV global longitudinal strain was similar between groups (NS). In multivariable regression analysis, reservoir LAS emerged as the strongest independent predictor of HFpEF defined by using both scores. Reservoir LAS with optimal cut off value of 24% showed sensitivity of 86% and specificity of 70% to identify high probability of HFpEF. Combination of LAS with NT-proBNP did not increase the accuracy of each parameter alone.

Conclusions

Reservoir LAS shows a strong independent association with probability of HFpEF in patients with dyspnea and paroxysmal AF. This advocates for more liberal use of LAS assessment to distinguish cardiac from non-cardiac dyspnea in patients with history of AF.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): International PhD programme in Cardiovascular Pathophysiology and Therapeutics (CardioPaTh).

Thermodilution-derived resting coronary flow measurement: “a reverse dose finding study”

Background

Hyperemic absolute coronary blood flow (in mL/min) can be safely and reproducibly measured with intracoronary continuous thermodilution of saline at room temperature at an infusion rate of 20 mL/min. This study aims at assessing the best infusion rate to measure resting flow by thermodilution, i.e. low enough to avoid microvascular dilation but high enough to allow reliable thermodilution tracings

Methods and results

In 26 coronary arteries (24 patients) with angiographic non-significant stenoses, absolute flow was assessed by continuous saline thermodilution at infusion rates of 10 mL/min and 20 mL/min using a pressure/temperature sensored guide wire, a dedicated infusion catheter and a dedicated software. Average peak velocity (APV) was measured simultaneously using an intracoronary Doppler-wire. In addition, in a subgroup of 10 arteries, absolute flow and APV were also measured during saline infusion at 6 ml/min and 8 ml/min.

In 26 coronary arteries there was no significance difference in the Pd/Pa and in the APV at baseline and during the infusion of saline at 10 ml/min (Pd/Pa: 0.94±0.057 vs 0.94±0.059, p=0.82; APV: 22.2±8.40 vs 23.2±8.39 cm/s, p=0.63). In contrast, at an infusion rate of 20 mL/min, we observed a significant decrease in Pd/Pa compared to baseline (0.85±0.089 vs 0.95±0.053 vs, respectively, p<0.001) and a significant increase in APV (22.2±8.4 cm/s to 57.8±25.5 cm/s, respectively, p<0.001). The coronary flow reserve (CFR) evaluated by Doppler and intracoronary continuous thermodilution correlated well (r=0.87, 95% CI = 0.72–0.94, p<0.001) and Bland-Altman analysis documented a mean bias of −0.003 (limit of agreement −1.05 to 1.04) thus indicating the presence of resting coronary blood flow during the infusion of 10 mL/min of saline. In 10 coronary arteries saline infusions at 6 and 8 ml/min did not produce any significant changes in the Pd/Pa and in the APV compared to baseline and both Doppler and Thermodilution derived CFR correlated well at each infusion rate (6 ml/min: r=0.71, 95% CI 0.14–0.92, p=0.02; 8ml/min: r=0.78, 95% CI=0.31–0.95, p=0.007). However, with an infusion rate of 6 mL/min, an unstable thermodilution tracing was observed. Accordingly, Bland-Altman analysis showed a significantly larger dispersion of the CFR values when 6 ml/min was used to measure resting coronary flow (as compared with 8 m/min): mean bias at 6 ml/min: −0.53, limits of agreement: −2.25 to 1.20: mean bias at 8 ml/min: 0.004, limits of agreement: −0.72 to 0.73.

Conclusion

Absolute resting coronary flow can be measured by intracoronary continuous thermodilution of saline at infusion rate of 8–10 ml/min.

Funding Acknowledgement

Type of funding source: None

Hyperemic hemodynamic characteristics of serial coronary lesions assessed by pressure pullbacks gradients (PPG) index

Introduction

The evaluation of functional significance in serial coronary lesions is crucial for achieving optimal clinical outcomes. In this setting, fractional flow reserve (FFR) measurements with pullback pressure recording can be helpful in assessing lesion functional significance.

Purpose

To describe the functional characteristics of angiography-defined serial coronary lesions using FFR-derived motorised pullback tracings, and to describe the Pullback Pressure Gradients (PPG) index - in these lesions.

Methods

Prospective, multicentre study with independent core laboratory analysis. Patients undergoing coronary angiography due to stable angina were enrolled. Serial lesions were defined angiographically as the presence of 2 or more narrowings with visual diameter stenosis >50% separated at least by 3 times the reference vessel diameter in the same coronary vessel. Continuous IV adenosine-FFR measurements were obtained using a motorised device at a speed of 1 mm/s. Pullback curves were assessed to determine the presence of focal step-ups (FFR >0.05 units over 20 mm). In addition, the PPGindex was computed for all vessels. PPGindex values close to 0 define functional diffuse disease whereas values close to 1 define focal disease.

Results

From a total of 159 vessels (117 patients), 25 vessels were adjudicated as presenting serial lesions (mean PPGindex 0.48±0.17, range 0.26–0.87). Two focal pressure step-ups were observed in 40% of the cases (n=10; mean PPGindex 0.59±0.17), whereas 8% of the vessels presented a progressive pressure losses (n=2; mean PPGindex 0.27±0.01). In the remaining 52% of the cases, a single pressure step-up was recorded (n=13; mean PPGindex 0.44±0.12; ANOVA p-value = 0.01). The PPGindex independently predicted the presence of two focal pressure step ups.

Conclusion

Hyperemic FFR curves in tandem stenoses revealed high prevalence of functional diffuse CAD. Two pressure step-ups occurred in less than half of the vessels. High PPG-Index identified vessels with two focal pressure drops. FFR tracings and the PPGindex provide a more objective CAD evaluation, which can lead to changes in the therapeutic approach.

Funding Acknowledgement

Type of funding source: None

Long-term outcome of minimally invasive mitral valve annuloplasty in disproportionate mitral regurgitation

Background

Hypothetical concept of disproportionate secondary mitral regurgitation (SMR) has been recently introduced to facilitate patient's selection for mitral valve intervention. However, real world data validating this concept are unavailable.

Purpose

To investigate long-term effects of minimally invasive mitral valve annuloplasty (MVA) in patients with disproportionate (dSMR) versus proportionate SMR.

Methods

The study population consisted of 44 consecutive patients (age 67±9,5 years; 64% males) on guidelines-directed therapy with advanced heart failure (HF), reduced LV ejection fraction (EF) (32±9,7%) and SMR undergoing isolated mini-invasive MVA. Patients with organic mitral regurgitation or concomitant myocardial revascularization were excluded. To assess SMR disproportionality, the PISA-derived effective regurgitant orifice area (EROA) and regurgitant volume (RV) were compared to the estimated EROA and RV by using Gorlin formula and pooled real world data.

Results

According to EROA, a total of 20 (46%) and 24 (54%) patients, respectively, had dSMR and proportionate SMR (pSMR). According to RV, a total of 17 (39%) had dSMR and 27 (61%) had pSMR. Patients with dSMR showed significantly lower prevalence of male gender and higher prevalence of diabetes mellitus than patients with pSMR (p<0,001). Moreover, we observed smaller LV end-diastolic volume, larger EROA and RV (both p<0,01) and higher LV EF (p=0,02) in the dSMR versus the pSMR group. Other baseline characteristics were similar. During median follow up of 4.39 y (IQR 2,2–9,96y), a total of 25 (56%) patients died from any cause while 21 (47%) individuals were readmitted for worsening HF. Patients with dSMR versus pSMR according to both EROA and RV showed significantly lower rate of HF readmissions (both p<0.05) (Figure 1, 2). In Cox regression analysis combining clinical and imaging parameters, dSMR was the only independent predictor of HF readmissions (HR 0.20, 95% CI 0.07–0.60, p=0.004). In contrast, mortality was similar between dSMR and pSMR (NS) with age as the only independent predictor (HR 1,10; 95% CI 1,03–1,18, p=0,003).

Conclusions

Minimally invasive MVA is associated with significant reduction of HF readmissions in patients with dSMR versus pSMR while the mortality is similar. This suggests the importance of other parameters, i.e. age and degree of LV remodeling, to guide clinical management in SMR.

Funding Acknowledgement

Type of funding source: None

Heart failure with preserved ejection fraction or non-cardiac dyspnea in paroxysmal atrial fibrillation: The role of left atrial strain

BACKGROUND

Diagnosis of heart failure with preserved ejection fraction (HFpEF) in patients with dyspnea and paroxysmal atrial fibrillation (AF) is challenging. Speckle tracking-derived left atrial strain (LAS) provides an accurate estimate of left ventricular (LV) filling pressures and left atrial (LA) phasic function. However, data on clinical utility of LAS in patients with dyspnea and AF are scarce.

OBJECTIVE

To assess relationship between the LAS and the probability of HFpEF in patients with dyspnea and paroxysmal AF.

METHODS

The study included 205 consecutive patients (62 ± 10 years, 58% males) with dyspnea (NYHA≥II), paroxysmal AF and preserved LV ejection fraction (≥50%), who underwent speckle tracking echocardiography during sinus rhythm. Probability of HFpEF was estimated using H₂FPEF and HFA-PEFF scores, which combine clinical characteristics, echocardiographic parameters and natriuretic peptides.

RESULTS

Patients with high probability of HFpEF were significantly older, had higher body mass index, NT-proBNP, E/e', pulmonary artery pressure and larger LA volume index than patients in low-to-intermediate probability groups (all p < 0.05). All components of LAS and LA strain rate showed proportional impairment with increasing probability of HFpEF (all p < 0.05). Out of the speckle tracking-derived parameters, reservoir LAS showed the largest area under the curve (AUC = 0.78, p < 0.001) and the strongest independent predictive value (OR: 1.22, 95% CI 1.08-1.38) to identify patients with high probability of HFpEF.

CONCLUSIONS

Reservoir LAS shows a high diagnostic performance to distinguish HFpEF from non-cardiac causes of dyspnea in symptomatic patients with paroxysmal AF.

P6316Hemodynamic response to rapid saline loading in heart transplant recipients

Introduction

A pulmonary capillary wedge pressure (PCWP) ≥25 mm Hg following volume load or exercise has been proposed as a partition value for detection of HfpEF. However, the hemodynamic response to volume challenge in heart transplant (Tx) recipients has never been studied.

Methods

24 heart Tx recipients (age: 65 years) with normal LV function (55±7%) and without rejection and graft vasculopathy underwent right heart catheterization to measure hemodynamic response to volume loading before and after a rapid saline infusion of 7mL/kg over 10 min. PCWP, right atrial pressure (RAP), mean pulmonary artery pressure (AP) were obtained and the PCWP and indexed (i) stroke volume (SV) data were used to construct Starling (SVindex/PCWP) curves. Pts were categorized in those with elevated filling pressures (Group A, n=13 pts) defined by a PCWP ≥15 mm Hg at rest or ≥25 mm Hg following volume loading vs those without (Group B, n=11 pts).

Results

No difference in age of donor and transplant heart, baseline hemodynamics and EF was noted between both groups. Saline infusion significantly increased PCWP and mean AP in both Groups (table 1) without any significant change in BP and heart rate. Interestingly saline infusion was associated with a significant rise in SV and SVi in Group B not in Group A pts. Moreover, in Group B pts the Starling curves revealed a larger SVi at any give PCWP compared to Group A pts (Fig.1).

Table 1 All (n=24) Group A (n=13) Group B (n=11) Baseline Volume Loading Baseline Volume Loading Baseline Volume Loading RAP (mm Hg) 5.3±4.1 9.2±4.8* 7.6±4.8 11.4±5.2* 3.8±2.5 7.3±1.9* Mean AP 18.4±5.4 24.1±5.9* 21.7±5.1 26.8±6.5** 14.9±2.4 20.8±2.6* PCWP 12.1±4.9 16.8±6.7* 15.0±4.9 19.8±6.5** 8.4±1.9 14.6±3.7* SV 71.4±19.6 72.5±23.6 73.2±6.2 72.4±6.2 69.2±14.6 79.2±3.9 SViml/m2) 37.4±9.2 37.9±11.2 36.7±7.1 38.7±9.9 35.3±6.0 40.5±5.2* *p<0.01 compared to baseline; **p<0.05 compared to baseline.

Figure 1

Conclusions

In the transplanted heart volume loading increases filling pressures and is able to unmask left ventricular diastolic dysfunction. Interestingly, those with HFpEF are characterized by a blunted Frank Starling response as evidenced by higher PCWP and failure to increase SV for any given PCWP. Further prospective studies are warranted to unravel the underlying mechanisms.

1156Coronary artery bypass grafting vs. FFR-guided PCI in diabetic patients with multivessel disease

Background

In diabetic patients with multivessel coronary disease (MVD), coronary artery bypass grafting (CABG) has shown long-term benefits in mortality over percutaneous coronary revascularization (PCI). Nevertheless, the impact of fractional flow reserve (FFR)-guided PCI on clinical outcomes has never been investigated in these patients.

Purpose

To evaluate the long-term (5-year) clinical outcome of diabetic patients with MVD treated with FFR-guided PCI compared to CABG.

Methods

From February 2010 to February 2018, all diabetic patients undergoing coronary angiography in one centre (n=4622) were screened for inclusion. The inclusion criterion was presence of at least two-vessels CAD defined as with diameters stenosis ≥50%. In case of intermediate coronary stenosis (%DS 30–70%), FFR was performed at the discretion of the operator. Revascularization was performed when FFR ≤0.80. Exclusion criteria were ST-elevation myocardial infarction, prior CABG, and moderate or severe valvular heart dysfunction.

To account for confounders, we compared outcomes by calculating an adjusted Kaplan-Meier estimator using inverse probability of treatment weighting (IPTW). Propensity score variables included age, sex, smoking habit, hypertension, hyperlipidemia, insulin therapy, family history of CAD, chronic obstructive pulmonary disease (COPD), glomerular filtration rate (GFR), prior myocardial infarction, peripheral vascular disease (PVD), admission for NSTEMI, ejection fraction, number of angiographic stenotic vessels. Odds ratios were calculated using generalized linear models (GLM). The primary endpoint was major adverse cardiovascular and cerebrovascular events (MACCE), defined as all-cause death, myocardial infarction and stroke. Secondary endpoints were the individual component of MACCE and any repeated revascularization.

Results

A total of 538 diabetic patients with MVD were included in the analysis. Among them, 317 (59%) patients underwent CABG and 221 (41%) FFR-guided PCI.

Patients treated with FFR-guided PCI had more often COPD as compared to patients in the CABG-group, but patients treated with CABG had lower GFR, more PVD, higher number of angiographic stenotic vessels (2.8±0.4 vs. 2.5±0.5; p<0.01) and higher Syntax score (20±7 vs. 14±6; p<0.01) as compared to the FFR-guided PCI group.

Clinical follow-up was obtained in 95% of the patients at a median follow-up of 5 years.

The incidence of MACCE was similar in the CABG and in the FFR-guided PCI group [27% vs. 29%; OR (95% CI) 1.05 (0.68–1.63); p=0.74]. No differences were found in the individual components of MACCE. Repeat revascularization was more frequent in the FFR-guided PCI group than in the CABG group [27% vs. 7%; OR (95% CI) 4.3 (2.35–7.9); p<0.01].

Conclusions

In diabetic patients with MVD undergoing FFR-guided PCI, no differences in major adverse events were observed at a median follow-up of 5 years compared with CABG.

279Clinical outcome after coronary bifurcation stenting: a systematic review and network meta-Analysis of PCI bifurcation techniques comprising 5572 patients

Background

The optimal PCI technique for bifurcation lesions remains a matter of debate. Several RCT have compared different bifurcation PCI techniques. Provisional stenting has been recommended as the default technique for most bifurcation lesions. However, emerging data suggests that double-kissing crush technique can be considered in true left main bifurcation lesions and has been endorsed by the European Society of Cardiology Guidelines.

Purpose

To compare the clinical outcome between different bifurcation PCI techniques.

Methods

We searched MEDLINE for randomized clinical trials (RCT) comparing PCI bifurcation techniques for coronary bifurcation lesions. Outcomes of interest were major adverse cardiovascular events (MACE) defined as the composite of cardiac death, myocardial infarction (MI) and target vessel or lesion revascularization (TVR/TLR), and the individual components of MACE. Stent thrombosis was assessed as defined by the ARC. Stratification based on left-main or distal bifurcations was performed. We evaluated the studies' risk of bias in accordance to the Cochrane Handbook for Systematic Reviews of Interventions, and certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation framework. We estimated summary odds ratios (ORs) using pairwise and Bayesian network meta-analysis.

Results

We identified 263 studies and of these included 19 RCT including 5572 patients treated with 5 bifurcation PCI techniques namely provisional stenting, systematic T-stenting, crush, culotte and double-kissing crush. Median follow-up was 12 months (IQR 8 to 36). When all bifurcation lesions were combined, double-kissing crush technique reduced the occurrence of MACE (OR 0.42; CrI 0.28 to 0.61) compared to provisional stenting. This difference was driven by a reduction in TVR/TLR (OR 0.39; CrI 0.25 to 0.65). No differences were found in cardiac death, MI or stent thrombosis among analyzed PCI techniques. No differences in MACE were observed between provisional stenting, systematic T-stenting, crush. In distal bifurcations (n=17 studies, 4634 patients), double-kissing crush also showed to reduce MACE (OR 0.48; CrI 0.29 to 0.67 vs. Provisional). In left-main bifurcations (n=3 studies, 938 patients) no differences in MACE were found between PCI techniques.

Conclusions

In this network meta-analysis, PCI bifurcation techniques were similar with respect to the occurrence of cardiac death, myocardial infarction and stent thrombosis. When all coronary bifurcations were combined, an advantage of double-kissing crush was observed in terms of MACE driven by lower rate of repeated revascularization. Further studies are required to define the best PCI bifurcation technique for left main coronary artery disease.

P854Physiological patterns of coronary artery disease

Background

Randomised controlled trials have confirmed the clinical benefit of invasive functional assessment to guide clinical decision making about myocardial revascularisation in patients with stable coronary artery disease. Treatment decision is based on one FFR value which provides a vessel-level metric as a surrogate of myocardial ischaemia. Also, the distribution of epicardial conductance can be evaluated using an FFR pullback manoeuvre.

Purpose

The objective of the present study is to characterise the physiological patterns of CAD using motorised coronary pressure pullbacks during continuous hyperaemia in patients with stable coronary artery disease.

Methods

Prospective, multicentre study of patients undergoing clinically-indicated coronary angiography. A pullback device, adapted to grip the coronary pressure wire, was set at a speed of 1 mm/sec. The pattern of CAD was adjudicated by visual inspection of the FFR pullback curves as focal, diffuse, or a combination of both mechanisms. Also, a quantitative classification of the physiological pattern of CAD was performed based on (1) the functional contribution of the epicardial lesion in relation to the total vessel FFR (Δlesion FFR/Δvessel FFR) and (2) the length (mm) of epicardial coronary segments with FFR drops in relation to the total vessel length. The combination of these two ratios, namely, lesion-related pressure drops (%FFR-lesion), and the extent of functional disease, resulted in the functional outcomes index (FOI), a metric that represents the pattern of CAD (i.e. focality or diffuseness) based on coronary physiology. Agreement on CAD patterns and between observers was assessed using Fleiss' Kappa. Analysis of variance (ANOVA) was used to compared quantitative variables. Correlation between variables was assessed by the Pearson moment coefficient.

Results

One hundred and fifty-eight vessels were included; 984,813 FFR values were used to generate the FFR pullback curves. Using motorised FFR pullbacks, 34% of the vessel disease patterns (i.e. focal, diffuse or combined) were reclassified compared to conventional angiography. The mean contribution of the angiographic lesions to the distal FFR (%FFR-lesion) was 61.7±25% whereas vessel length with the physiological disease was 59.8±21% of the total vessel length. The mean FOI was 0.61±0.17, and differentiated focal from diffuse CAD in terms of %FFR-lesion (p<0.001) and physiological extent of CAD (p<0.001).

Conclusion

Coronary angiography was inaccurate to assess the patterns of CAD. The inclusion of the functional component reclassified 34% of the vessel disease patterns (i.e. focal, diffuse or combined). A new metric, the FOI, based on the functional impact of anatomical lesions and the extent of physiological disease, discriminated focal from diffuse CAD. Further clinical trials are required to evaluate the usefulness of FOI for clinical decision making and outcomes.